1. Field of the Invention
The invention relates to a tandem roadwheel system as employed on a construction vehicle such as a motor grader.
2. Prior Art
A motor grader is ofttimes operated on uneven terrain whereby the tandem roadwheels on one lateral side of the vehicle are displaced vertically relative to the tandem roadwheels mounted on the opposite lateral side of the vehicle. Also, the tandem roadwheels on one side of the vehicle may individually be placed at different vertical positions relative to one another because one of the roadwheels may be riding over a rock, dipping into a ditch or the like. The resulting tilting of the vehicle may thus give rise to operational problems such as reduced tractive effort of the vehicle and a reduction in drawbar pull. In addition, conventional tandem mounted rubber tires employed on conventional motor graders essentially function as undamped springs which would not provide the suspension properties desired for earthworking operations. Further, equal roadwheel loading is generally not provided under all conditions in a motor grader. Still further, motor graders normally do not provide means for levelling the main frame and operator's station structure when the vehicle is traversing an angled side slope for the purpose of grading it. This causes operator discomfort and resulting decreased productivity.
Motor graders are generally articulated between a first pair of steerable roadwheels and a tandem roadwheel arrangement. Generally only the first pair of roadwheels are steerable whereby the articulation is desirable. This of course increases the cost of the vehicle as well as providing several structural problems such as passing hydraulic lines and mechanical connections across the articulation. It would be advantageous to have a motor grader which was built with a non-articulated frame and whereby steering thereof could be accomplished by making not only the first pair of roadwheels steerable but also the tandem roadwheel arrangement thereof. It would be even more advantageous if this could be accomplished in a relatively straightforward manner and via a relatively rugged structure.